1. Field of the Invention
The present invention relates to a baffle for an automotive fuel tank and, more particularly, to a baffle for an automotive fuel tank that can be firmly fixed in the fuel tank and prevent flow noises effectively.
2. Description of Related Art
In general, a fuel tank for storing fuel to be supplied to an engine is established in an automotive vehicle. Since the fuel tank is of a generally rectangular shape made of a thin steel sheet having a predetermined volume, fuel sloshing occurs in the fuel tank when the vehicle suddenly starts or stops. Such fuel sloshing is a nonlinear flow phenomenon caused by the fuel in the fuel tank, in which a free surface exists, due to the vehicle movement.
It has been known that the fuel sloshing in the fuel tank occurs most frequently when the fuel amount is about 50-70% and noises generated by the sloshing can be classified into the following three kinds: (1) an impact noise created as a fluid collides with the wall surface of the fuel tank due to the sloshing; (2) a fluid collision noise produced when a hydraulic jump occurs due to the sloshing in the fuel tank and a portion of the fluid separated from the hydraulic jump collides with the fluid forming the free surface; and (3) a noise generated when cavitation and bubbles produced during the fluid collision are burst.
The sloshing noises of the automotive fuel tank as described above have been pointed out as a problem since for a long time. However, it has been treated indifferently since it does not have a significant effect compared with the other noises produced in the entire vehicle. Since deformations of the fuel tank, noises and quakes may occur if impacts are applied continuously to the wall surface of the fuel tank due to the above-described sloshing phenomenon, various methods for buffering the flow impact of the fuel for the wall surface of the fuel tank to reduce the noises have been adopted.
In general, the most widely used method for removing the noises caused by the sloshing is to establish a baffle having a plurality of through holes in the fuel tank. In case of a fuel tank made of steel material, a plurality of baffles having through holes is arranged in the vertical or horizontal direction in the fuel tank to prevent the fuel stored in the fuel tank from sloshing. Such baffles made of metal material are fixed via a spot welding on the inside surface of the fuel tank.
In such method, it is possible to fabricate the baffles in desired shape and size and readily established the same in the fuel tank. However, the manufacturing cost and the weight increase are excessive and, especially, it causes a problem in that a fuel leakage can occur due to corrosions in the regions where the spot welding has been made for fixing the baffles. Moreover, since the impact force due to the fuel flow is transferred directly to upper/lower panels of the fuel tank, the baffle may be separated from the fuel tank as the welded regions receive concentrated stresses.
In case of a fuel tank made of plastic material, it is possible to prevent the generation of the fuel flow noises to some degree due to its material properties. However, it is impossible to establish the baffles in a desired shape or size since it is fabricated via a blow molding and, accordingly, does not have a structure in which the upper/lower panels are not separated like the fuel tank of steel material. Instead, a fuel tank of plastic material may be formed with a structure similar to a baffle in a method of protruding a specific region internally in the fuel tank during the molding process. However, there are limitations in preventing the fuel flow and the noises through the above method. Thus, another technique that has been used is a method of inserting a sponge baffle of an open cell type into a portion of a fuel tank. Materials such as polyurethane, for example, having excellent fuel resistance and restoration performance and has a structure in which a plurality of pores is used. However, the sponge baffle is not firmly fixed in the fuel tank and when separated also has limitations in preventing the flow noises.